Fluorescent lighting fixtures employing tubular lamps adapted to be held in resilient contacts at opposite ends of a fixture are often shipped from a fixture manufacturer to stores for resale to consumers with the lamps connected to the fixture. All that need be done to use the fixture is to hang it and connect a power cord to an AC supply line. The resilient contacts which grasp the pins of the lamp are normally strong enough to support the weight of the lamp. However, during shipping, the rough handling to which packaged fixtures are sometimes subjected is sufficient to impart forces to the lamps which cause them to come out of the contacts resulting in breakage and its attendant expense and inconvenience.
In some environments, fluorescent light fixtures in situ are subject to abnormal vibration as, for example, in areas susceptible to earthquakes and construction sites where blasting is being done or vibration transmitting machinery such as pile drivers is being used.
The foregoing problems have created a need for a fluorescent lamp holder wherein a lamp, once inserted, cannot inadvertently be shaken loose of the holder yet can be removed when it is desired as, for example, when replacing a burnt-out lamp, with facility. Fixtures are known in the prior art wherein a fluorescent tube is inserted into a circular channel, one pin at a time, and then rotated until it is locked in place. Such lamp holders are of questionable effectiveness in preventing a lamp from inadvertently coming out of the lamp holder and many people find it difficult to properly insert or remove a lamp from this type of lamp holder.
Lamp holders employing parallel channels with resilient grasping contacts disposed therein to permit the two pins at each end of the lamp to be forced into the channels and there grasped have been found much easier to use. The problem of lamps inadvertently coming out of this type of holder has been addressed by a device disclosed in U.S. Pat. No. 3,851,295 to Geier for Self-Locking Lamp Holder. Geier employs a relatively complex device using a spring and plunger mechanism internal to the lamp holder. This requires a special lamp holder construction which substantially increases the cost of the lamp holder. Neither Geier nor any of the known prior art devices provide an effective means for selectably locking and unlocking a lamp in place in a fluorescent light fixture without major and costly modification of the basic standard lamp holder design. The invention disclosed and claimed herein fulfills this need.